1. Field Of The Invention
This invention relates to the general art of float switch assemblies and more particularly to magnetically actuatable float switches intended for use with pumps. Although the float switch assembly can be used with submersible and non-submersible pumps as well, it is described herein with specific reference to the operation of submersible pumps as the preferred use of the invention. The switch in its most preferred embodiment is characterized by providing it in a hermetically sealed compartment along with a permanent magnetic body and twin armatures adapted to sequentially "make" or "break" electrical contacts in an electrical circuit, and a contact-actuating mechanism.
2. Description Of The Related Art
Sump pumps and the like generally use two types of switching mechanisms. One type is a tethered cord float switch. A drawback of this type of switch is that to increase the pumping differential, the length of the cord must be increased. This can be problematic if the pump is to be operated in smaller diameter sumps, for example, as the tethered cord switch would not have enough room to operate adequately and could possibly cause the float to hang up. To overcome this problem, some sump pump manufacturers rigidly attach a rod mounted vertically along the outer pump housing. A float with a hollow center rides up along the rod and at a certain height will actuate a switch, turning on the pump. As long as the pump can fit in the sump, there should be no interference. Examples of this type of pump and switch arrangement are found in U.S. Pat. No. 1,170,377 to Weed and U.S. Pat. No. 1,838,135 to Derby.
Float switches having a magnetic arrangement of sorts at the upper end of the rod for actuating a contact switch have been described in U.S. Pat. No. 2,726,296 to Hanson, U.S. Pat. No. 4,647,740 to Hanson III, and U.S. Pat. No. 4,865,073 to Kocher.
Operation with a sump pump requires equipment that will assure certainty of operation over long periods of time. This invention fulfills a need which has developed for an improved magnetically actuatable float switch assembly for use with sump pumps, and the like. In its most preferred form it also provides a hermetically sealed environment for the electrical contacts and the contact-actuating mechanism, thereby assuring a longer operating life, greater reliability and less wear and tear on parts of the switch assembly.